If you want to know more about geology, here are some interesting links:

http://geology.com/ is full of great articles and pictures 

http://geology.usgs.gov/  should convince you about the critical role of geology in crucial fields such as mineral exploration and hazard prediction and management

http://www.sciencedaily.com/news/earth_climate/geology/ is great if you want to keep yourself up to date with geological discoveries 

If you are still wondering what geology is, have a read at http://en.wikipedia.org/wiki/Geology 

 
Glossaries: 

http://wrgis.wr.usgs.gov/parks/misc/glossarya.html provides an excellent glossary of geological terms 

http://www.webref.org/geology/geology.htm is a bit more technical

http://start1g.ovh.net/~geopedia/#menu is a fairly simple glossary (only in French, though)